Infection is the invasion and establishment of a foothold for growth in an organism by a pathogenic microorganism (hereinafter called bacterium). Whether an infection results in the outbreak of disease depends upon the interrelationship between the resistance of the host and the virulence of the bacterium.
Bacteremia may result from infection by one or more specific bacteria. Improvement in the methods of treatment of bacteremia is an important issue as shown below:
Bacteremia is not a disease caused by a specific bacterium. It is caused by the emergence and habitancy of various bacteria in blood. Its onset is clinically suspected when fever of about 40.degree. C. persists for two or more days. Bacteremia is a serious and urgent disease, of which the primary symptom is a high fever. A patient may die within several days if not properly treated. If a patient is an infant or is suffering from terminal cancer with weakened resistance, the patient may die in one or two days.
In the case of bacteremia, phagocytes including neutrophils, ,monocytes, and macrophages primarily work in defense of the body.
Emergence of bacteria in the blood of a patient suffering from bacteremia is to the invasion of bacteria, which have avoided degradation by the phagocytes, from the tissue into the blood.
Bacteremia is a state after the above-mentioned condition has been reached. To treat bacteremia, a large amount of antibiotic to which the causative bacterium or bacteria is sensitive is administered.
Generally speaking, however, antibiotics lower the functions of the body such as the liver. Therefore, one must carefully avoid administration of an ineffective antibiotic to a patient who is seriously ill.
Bacteremia is defined as a case when the phagocytesis of cells is not able to overcome the virulence of bacteria and the bacteria spread in blood throughout the body. Sepsis is a bacteremia with serious symptoms due to toxins produced by the bacteria. Proof of sepsis (or establishment of the diagnosis) requires four important factors: 1) clinical symptoms; 2) culture; 3) gram-staining; and 4) shock state. The line of treatment is determined on the basis of these factors.
It, therefore, is essential to quickly and reliably identify the bacterium (bacteria). (The Conventional Methodology) Currently, in detection and identification of bacteria in a bacteremia-suspected specimen in a laboratory, it is a common procedure to make identification in selective media only after the specimen has been found positive in a routine process of culture bottle (hereinafter referred to as "C.B."). The rate of successful culture of bacteria from these blood specimens, however, is extremely low. Moreover, if a large dose of antibiotics is administered when bacteremia was suspected, bacteria, if any, in the blood will not be cultured and grow in many cases. The rate of C.B. positive cases, therefore, is extremely low.
Available sub-routine methods include instrumental analysis of constituents and metabolic products of bacteria (Yoshimi Benno, "Quicker identification of bacteria with gas chromatography", Rinsho Kensa, Vol.29, No.12, November 1985, Igaku Shoin), a method utilizing specific antibody (Japanese Patent Provisional Publication No. 60-224068), and a method based on hybridization based on specificity of DNA (Japanese Patent National Publication of the translated version No. 61-502376) which has a high accuracy due to the specificity. Separation and cultivation of a bacterium or bacteria, however, are essential pretreatment for all of these methods.
On the other hand, there is a method established based on the function of phagocytes In infectious diseases. According to that method, a stained smear of bully coat in which leukocyte of the blood sample is concentrated is examined under an optical microscope.
Generally speaking, in adult bacteremia patients, the rate of detection of bacteria in bully coat specimens is 30% at most which is identical to that in earlobe blood specimens. For newborns, however, it was reported that bacteria had been detected in 7 cases out of 10 cases (70%). The information concerning the presence of a bacterium or bacteria in peripheral blood, which is available through microscopic examination of a smear, is an important guide for treatment.
Although diagnosis of bacteremia require quick and reliability of the methods, the conventional methods hardly contribute to the treatment.